This invention relates generally to pinch diodes and especially to an improved diode which produces an intense electron beam pinch and efficiently propagates the beam energy along the anode.
The efficient propagation of an intense electron beam is highly desirable for many reasons, among which are the abilities to apply the energy of the beam at a sufficient distance to avoid damage to the power source, and to confine a target to a specific location. Such features are especially important, for example, in order to irradiate a solid target pellet for material response studies, to produce and heat high-temperature plasmas, and to produce an intense localized source of x-rays.
Existing devices for producing an intense flow of electrons include the dielectric-rod-cathode diode (Bennett diode), the planar and hemispherical pinched electron beam diodes, and planar diodes with exploding wires on axis. These devices propagate electron beams with very low efficiency, typically on the order of only a few percent over distances greater than or equal to 10 centimeters. External techniques for propagating beams outside of these devices include exploding-wire discharge channels, z-pinch discharge guides and laser-initiated discharges. These techniques guide the beam through a preformed plasma discharge. However, the propagation efficiency reported for these techniques does not exceed 50%. Moreover, these techniques usually require large, expensive, and complex external equipment.
Pinch propagation along rod--and cylindrical-shaped anodes of a diode for producing a multimicrosecond pulse of x-rays has been observed by K. F. Zelenskii, O. P. Pecherskii, and V. A. Tsukerman (Soviet Physics-Technical Physics, Vol. 13, No. 9, March, 1969, pp 1284-1289). The Zelenskii et al. device operates at high impedance (approximately 200 ohms) and the anode includes a cylinder having either a small constant radius which provides a slow pinch formation and very low currents, or a large constant radius which results in higher current but slow pinch propagation and low current density. Although that device forms an anode surface plasma, the anode, because of its shape and material, may not produce high ion fluxes, fast pinch formation and propagation, or operate at low impedance. In addition the metal cathodes of that device do not emit electrons rapidly enough in that configuration for operation with applied voltage pulses shorter than 0.1 microsecond.